Signaling system



D. F. WHITING.

SIGNALING SYSTEM.

APPLICATION FILED 050,26, 1919.

Patented May 17, 1921.

UNITED STATES PATENT OFFICE.

v DONALD F. WRITING, OF NEW .YORK, N. -Y., ASSIGNOIETO WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION 01 NEW YORK.

SIGNALING SYSTEM.

Specification of Letters Patent. P t t M 7, 1921;

Application filed December 26, 1919. Serial No. 347,409. i

To all whom it may concern:

Be itknown that I, DONALD F. WHITING a citizen of the United States, residing at New York, in the county of Bronx, State of New York, have invented certain new and useful Improvements in Signaling Systems, 7 of which the following is a full, clear, con- Y ever, be rendered eflicient for transmit-.

ting currents of the other frequencies. by connecting into the lines, in suitable relation, other elements of inductance or capacity or by changing the yalue or rela tion ofexisting elements. The present invention contemplates providing in a system of this character means responsiveto currents of other frequencies transmitted over a line for altering the character thereof, to make it more efficient for transmitting-c111?- rentsof such other frequencies. The 1nven-- tion in the present application is illustrated as applied to a telephone transmission line containing an amplifier for amplifying both talking andsignaling currents and ar j ranged normally to be eflicient for transmitting talking currents, to provide for altering the condition of the line when signaling current is transmitted.

For a more complete understanding of this invention, reference should be had to the following description considered in connection with the accompanying drawing,

which shows diagrammatically the equipment at a repeater station of a two-wire-telephone-repeater circuit containing an emodiment of this invention. In the drawing there are shown two line sections 20 and 40 in each of which are connected 'the secondary windings of output repeating coils 2 1 and 41, respectively.

secondary windin Connected with the. line section are 'artificial lines '22 and 42 for balancing the respective line sections with respect to out-, going currents. An amplifier 23' of the penal construction for amplifying both talkmg and signaling currents has its input circult connected through an input repeating coil 24 and through a balanced potentiomneter 25 to-the' line section 20, the connection being at the mid-point of the secondary windin s of the output coil 21. The potentlome er is for the purpose of controlthrough' the. coil 24 ,to the input circuit of the ampllfier 23. The outp itcircuit' of the amplifier 23 is connected with the ,primary ling the amount of talking current admitted I I winding ofthe output repeating coil 41 whose are connected in the li'nesection 40. In a similar manner the input circuit of an amplifier 43 is connected through an input repeating coil 44 and a balanced potentiometer 45 with the line seetion 40, the outputv circuit thereof being a connected with the primary'winding of theoutput repeating .coil 21 whose secondary windings are connected in line section .20. A condenser 26 connected in the middle of. the potentiometer bridge- 25 is of low imped'ance to talking; currents and is of such capacity that it forms withv the winding of a ringing response signal controlling relay 27, connected in parallel therewith, a loopc1r-.

cuit tuned to the frequency. of the ringing or signaling currents." The ringing response relay 27 controls the normally energized switching. relay 28 WhlCh, when. de-

energized, connects a condenser 29 in par- 'allel with the primary windings of themput repeating coil 24 to form a loop circuit tuned to the frequency of thejsignalmg curs rent, and short-circuits the primarywinding pfthe input repeating coil 44thereby preventing signaling current traversing the a line section 40 from beingrepeated back into the line section 20'when signaling current is incoming over the line section 20. Condenser 46 and ringing response rehy 47 are similarly connected with POtGIltlOIIlG- ter 45, and relay 47 similarly controls a 's'witching relay 48. Relay 48, 1n releasing,

connects a condenser 49 in parallel with the I primary Winding of the input repeating coil 44 to form a loop circuit tuned to the frequency of the signaling current, and shortcircuits the pri ary winding of the in ut repeating coil 24. Condensers 30 and prevent the fiow of direct current through the primary winding of the respective output coils 21 and 41.

responsive to currents of the talking frequencies.

Talking currents incoming over the line section 40 will be amplified by the amplifier 43 and transmitted into the line section 20 in a similar manner without affecting the ringing response relay 47 Signaling current incoming over the line section 20 passes into the input circuit of the amplifier 23 in the same manner as talking currents admitted thereto and the amplified signaling currents are transmitted through the repeating coil 41 to the line section 4Q. The, condenser 26 is of high inipedance to currents of the signaling frequency, and the loop circuit formed by the condenser 26 and the winding of the ringing response relay 27 becomes effective when s'ignalingcurrent is impressed upon the terminals of this circuit so that currents are set up therein. These .large currents which apparently oscillate when a comparatively small amount of current of the proper frequency is applied to the terminals of theiloop are the result of resonance occurring, in the loop. The action taking place may be explained in the fol-' lowing manner.

The current flowing through relay 27 lags behind the applied electromotive force by a considerable phase angle. This current may be considered as consisting of two components, one in phase andto'ne in quadrature to the applied electromotive force. The current flowing through condenser 26' consists mainly of one component Wl11Ch is in quadrature phase relation to the applied electromotive force and 'leading the latter approximately-90 degrees. At, resonance the two quadrature components. of currents are. mutually opposite-'in phase'and equal in magnitude and therefore nullify one another when flowing in the same' circuit. Therefore, the current flowlng into the terminals of the loop cir cuit i s'the in-pha'se component only of the current passing through the winding of relay 27. Thus with a constant valueof electromotive force applied across the winding of relay 27, the current entering the'circuit is decreased in value and brought into phase with this applied electromotive force by the application of the condenser 26 of the proper value. This decrease of current with a given applied electromotive force is equivalent to an increase in the'ef fective resistance of the relay, and this increase is efl'ected with no loss of energy. Because of this increasein the effective resistance of the loop circuit including the relay (at the resonant frequency), the relay receives a greater proportion of the total energy flowing about the circuit of which the loop circuit is a part, resulting in a considerable amount of discrimination in favor of that frequency. This loop circuit therefore presents a comparatively high impedance to currents of signaling fre-' quency impressed upon its terminals. This impedance is muchmore that that of either the condenser or the relay forming the loop. Therefore, when signaling current is transmitted, the tuned circuit becomes effective to practically open-circuit the potentiomewinding of repeating coil 24 is similarin every detail to the effect of the condenser 26 upon the winding of relay 27 as previously explained. The effective resistance of" the loop; circuit containing condenser 26 and the input, coil 24 is thus'raised by means of resonance until it is approximately equal to the effective resistance of the circuit joined thereto, this condition resulting in the maximum transmission of currents of the signaling frequency into the amplifier-'23. The closure of'the righthand contact of relay 28 short-circuits the primary winding of a the input repeating coil 44 thereby preventing any signaling currents which may pass through the potentiometer 45 due" to any unbalance between the line and section 40 and its artificial line 42 from passing into the amplifier 43. Upon the cessation of signaling current over the line section 20, relay 27 releases and relay 28 operates, restoring the circuit to normal condition. When ringing or signaling currentis incoming to the repeater station over the line section 40,the relays 47 and 48 function ina manner similar to relays 27 and 28 and the incoming signaling current is amplified and transmitted into the line section 20 in the same manner as described for current incoming in the opposite direction.

What is claimed is:

' 1. In a signaling system,'in combination,"

two line sections, an amplifier for amplifying talking and signaling currents whose output circuit is connected with one line section, an input transformer connecting the input circuit of the amplifier with the other line section, means associated with the other line section for controlling theamplification of the amplifier to currents of talking frequencies, a loop circuit tuned to current of the signaling frequencies associated therewith and rendered efiective when signaling current is impressed upon the terminals 1 quencie's, a loop circuit tuned to currents of the signallng frequency and rendered effec tive when signaling current is impressed upon the terminals thereof to alter the effect of the amplifier controlling means at signaling frequency, a relay in the loop circuit, and a condenser connected in circuit with the primary winding of the repeatingcoil by the operation of the relay to form alsec- 0nd loop circuit tuned to currents of the signaling frequency.

3. In a signalmg' system, in combination, line sections over which both talking and signaling currents are transmitted, a repeating coil joining the line sections, current regulating means in circuit with one line section for controlling talking current admitted to the repeating coil, .a condenser in circuit with the current regulating means,

a relay in parallel with the condenser and forming therewith a loop circuit tuned and rendered effective by signaling currents impressed upon the terminals thereby tolalter the effect of the current regulating means at signaling frequency, and a condenser connected in circuit with a winding of the repeating coil by the operation-of the relay to form a second loop circuit tuned to signaling currents.

4. In a signaling system, in combination,

two line sections, two repeaters for amplifying talking and signaling currents, each repeater having its output circuit associated withone line section, a repeating coil for each line section, each connecting with one line section-the input circuit Ofr the repeater whose output circuit isassociated with the other line section, current regulating means associated with each line section for controlling talking current admitted to the .as-

'sociated repeating coil, a loop circuit tuned to currents of the signaling frequency associated with the current regulating means and rendered effective when signaling our rent is impressed upon the terminals thereof to alter the effect of the current. regulating means in response to signaling currents, and means included therein and responsive to such impression of the signaling current to establish a short circuit of the line winding of the repeating coil connected with the other section.

In witness whereof I hereunto subscribe my name this 23rd day'of December, A. D 1919. v

DONALD F. WHITING. 

